This finely machined mount of the hardest aircraft aluminum available will install quickly on your K31 receiver, requires no alteration to the rifle and can be removed and reattached with a true return to zero. The 3/8" rail allows for clean ejection of expended brass and will not interfere with bolt handle operation. The clamp mechanism is steel. Mounts you finest scope with any 3/8" rings. Accepts any standard rimfire/airgun rings (not included - sold separately) (3/8” dovetail), available from Graf & Sons from a variety of manufacturers.